This invention relates to a passenger protection apparatus which is operated at the time of collision of a vehicle such as an automobile.
There are many conventionally known passenger protection apparatuses comprising passenger protection means as described below for maintaining a passenger's posture at the time of collision of a vehicle. As passenger protecting means, there is known, for example, an air bag apparatus in which an air bag is provided in a position in front of the passenger such as in a steering wheel or in a dashboard such that the air bag is inflated at the time of collision of the vehicle. There is also known a seat belt retraction apparatus for rapidly retracting a seat belt.
In case plural kinds of passenger protection means are mounted on the vehicle, it is known to set levels of actuation at the time of collision of respective kinds to values which are different from each other so that, in a light degree of collision, the passenger protection means are only partially actuated or operated to reduce the repair expenses. In case the passenger protection means is actuated by gas pressure to be generated by a gas generating device, it is known to provide a plurality of gas generating devices for one piece of passenger protection means and to vary the levels of actuation of the plurality of gas generating devices so that, in a light degree of collision, the gas generating devices are only partially actuated. This partial actuation of the gas generating devices is to restrict the actuation speed of the passenger protection means so that its operation is in agreement with the sense of collision to be actually perceived by the passenger.
Where the collision of the vehicle is of such a degree that the passenger protection means are only partially actuated as described above, there may be a case where the vehicle can still travel by its own driving force. When the vehicle were to be collided for a second time during the travel after the first collision, there will be no problem from the viewpoint of the passenger's safety because the remaining part of the passenger protection means will be actuated to protect the passenger. However, the actuation level of the remaining part of the passenger protection means is actually set to a level which is higher than the level actuated at the time of the first collision. It is, therefore, preferable to cause the remaining part of the passenger protection means to actuate at a level which is lower than the originally set value in order to give the passenger a sense of assurance.
Further, also in case where a plurality of gas generating devices are provided for one piece of passenger protection means, when the vehicle were to be collided for a second time after the plurality of gas generating devices have been partially actuated in the first collision, there will be no problem because the remaining part of the gas generating devices will be actuated. However, the sense of assurance on the part of the passenger can further be increased if the level of actuation of the remaining part of the gas generating devices is lowered.